Oscar FX: Building a Better Rome

Rome wasn't built in a day, nor were the dazzling special effects in Ridley Scott's Gladiator, one of the films up for Academy Award honors for Best Visual Effects.

Scott recreated the drama and pageantry of ancient Rome and games at the Colosseum with computer generated imagery, or CGI, that was not available for the sword-and-sandal epics of the 1950s and '60s.

Gladiator's special effects artists worked hand in hand with the production designer and cinematographer to create epic visions of Roman architecture and German battlefields, and even populating them with thousands of digitally created or manipulated extras.

More than just eye candy, the seamless combination of CGI and a moving camera helps place the viewer right in the middle of the bloody action. "Where we pushed the limit [was by] applying modern camera work to an ancient event," said visual effects supervisor John Nelson. "Most FX people in the past would look at a 28-second Steadicam move around gladiators as a visual effect and say, 'What, are you crazy?'"

A stunning example of the marriage of principal photography and computer graphics is the entrance of gladiator Maximus Meridius into the Colosseum for the first time. "It was always our concept to treat the Colosseum like it was the Super Bowl," Nelson, said, "in that you're going out on the field with the players and you have 40,000 people screaming for your head — it must have been intimidating!

"Ridley is such a dynamic cinematic director [who believes] if a shot is more dynamic by making it move, then by all means it should be moving even if it's a visual effects shot," Nelson said. "For that shot, at first Ridley wanted to come out and look up into the valerium [the sun shades erected like a roof on the top of the arena]. And I posed the question to him: 'What would you do if we were really back in the arena and it wasn't just an effects shot that we had to make up?' And he said, 'Well, if that were the case then I would do a full Steadicam move all around the actors.' And I said, 'Why don't we do it?'"

The 28-second, 540-degree shot begins behind the actors running onto the arena floor, then circles around them as they gaze up at the stands, revealing seats, arches, and thousands of spectators. "I like the idea because its really puts the audience in it — plus as far as showing the Colosseum we will have laid it all out in the first shot. Sort of swinging for the fences."

The set of the Colosseum, built near the sea in Malta, only rose about one story, and didn't even make a complete oval. For shooting closeups of gladiatorial combat or of the crowd giving a "thumbs up" or "thumbs down," that was sufficient. But for a wide-angle shot that would reveal the upper reaches of the Colosseum, a virtual set was required.

To build a 3-D Colosseum in the computer, Nelson and his crew used the blueprints of production designer Arthur Max, who constructed the partial life-size set. "We then photographed the textures and the actual patina and stucco used on the Colosseum itself. Basically we projected those textures onto our digital Colosseum — we glued them in place," Nelson said.

"Not only did we extend up the two floors that were missing [from the practical set], we built the back end of the Colosseum that didn't exist, we built the roof, we put people on the roof, and built the outside as well."

Video: Click Here to see raw footage of the gladiators' entrance into the arena; computer compositing of spectators; rendering of the Colosseum; inserting crowds in the stands; compositing backgrounds with the principal actors; and the finished shot.

Friends, Romans, Countrymen, Lend Me Your Bytes

Building a virtual Rome was one thing; populating it was something else. To fill the screen with teeming hordes of citizens, the FX crew used two different techniques involving scanning or mapping images of extras into a computer for further manipulation.

"I'm a big fan of being able to shoot real things, map them onto other things [computer models] and then move them around [within the image] and place them and re-light them," Nelson said. "So when you look at them they look real because they are real, but they're been rearranged inside the computer."

One method required extras to be shot from different angles on PAL video wearing blue fabric against a green background. The computer could then erase the green background and replace the fabric color with any wardrobe color of the artist's choosing. That "paper doll"-like Roman could then be placed anywhere within the frame. "We had discrete control over each person. So we could make the audience start cheering at the bottom and go to the top. We could have made them do the wave if we wanted them to."

Another technique involved taking still images of costumed extras and mapping them onto 3-D computer figures that could then be manipulated. "It's like taking a mannequin and projecting a slide on it, and sticking that texture to it," Nelson said.

"Then we used a technique called motion capture where we actually captured the actions of people walking, talking, leaning out doorways, waving at their friends, working on the roof, manning machinery. This data we used to animate the people, and the real textures we shrink-wrapped onto them provided the texture of their skin and clothing. And then we relit them and put them on top of the Colosseum, streaming in or hanging out in the streets, cheering as the chariots came in and whatnot."

Video: Click Here to see elements of the "Blimp Shot" — raw footage on location at Malta; CGI crowds; and renderings of buildings and the Colosseum.

There were a total of 90 FX shots in Gladiator. (Another 30 planned shots were cut when the movie was being trimmed down to 2 ½ hours.) "Some of the other films we're competing against have lots more FX shots, but very few films have a 26- or 28-second visual effects shot," Nelson said.

"That's inordinantly long because of two things: modern audiences are raised on MTV and commercials and they're used to incredible detail every one or two seconds; and also as you look at a visual effects shot you have a long time to pick it apart. So not only did our shots need to look good, they had to have incredible amounts of detail to sustain the screen time."

Pixelated Soldiers and Digital Firepots

Detail was key in the film's opening sequence, when General Maximus leads his army into battle in Germania. The filmmakers were limited in the number of extras they could hire, the number of catapults they could construct for the conquering army, and the size of the location (a forest in Surrey, England).

"Basically, in the old days, Stanley Kubrick would have hired the Spanish army to do that," Nelson said. "But you couldn't do it today, those shots would be too expensive."

To create a sweeping panorama of flames and carnage, the filmmakers shot live-action footage of the battle with a locked-off camera, then repositioned people and props for additional footage. The three static shots were then scanned into a computer, lens distortion from each frame was removed, and additional elements (such as hundreds of flaming arrows and firepots) were digitally inserted. Finally, the strung-together (or tiled) plates were used to generate a long camera pan across the raging battlefield, thereby making up for what the actual location lacked in size and danger.

The most unusual use of CGI came following the unfortunate circumstances of Oliver Reed's passing. The veteran actor, who played Proximo, died during shooting in Malta, with scenes left unshot. Some computer wizardry saved the show and helped rescue what was one of Reed's most notable performances.

"Pietro Scalia, the editor, pulled out performances of Oliver that he liked that we could sort of write a story around," Nelson said. "Those shots were used for the front-on closeups of Oliver. But we had to change his clothes, take him out of scenes, relight him, change his hair and even shave his beard, and then we put him in new backgrounds. And then for the wide shots we shot with the body double. In the big mix of what we did, it wasn't our most difficult work, but it was very important to the movie.

"Oliver was giving such a great performance," Nelson said. "All we did is really help him finish it."

Part Two: The Perfect Storm